The present invention relates to an intelligent cruise control system for a moving body. The cruise control system is capable of detecting a distance from the moving body to a car running ahead of the moving body or the speed of the preceding car relative to the moving body by means of a radar installed on the moving body or the like, allowing the moving body to accelerate and decelerate automatically so as to maintain a safe distance from the moving body to the preceding car.
An effort to put a so-called auto cruise control apparatus to practical use has been in progress since an early time and has become widely popular among general vehicles. The cruise control apparatus is a constant-speed running apparatus capable of automatically maintaining the running speed of a vehicle at a constant speed set by the driver in advance.
Even though auto cruise control apparatuses are built from different hardware, they have all but the same system configuration. That is to say, the system configuration of most auto cruise control apparatuses comprises: a controller for carrying out control so as to make the difference between a speed signal received from a speed sensor as a feedback and a target speed equal to zero; an actuator for adjusting the degree of opening of a throttle in accordance with a control signal output by the controller; and an operation switch for setting auto cruise control.
In addition, the operation switch has facilities including: a set switch for setting a target speed in the course of running; a cancel switch for canceling a set target speed; and a resume/coast switch which is used for implementing acceleration or deceleration by increasing or decreasing the target speed when the resume/coast switch is being operated (typically by being pressed) continuously during constant-speed running control.
However, the conventional technology described above has problems described as follows.
The auto cruise control apparatus is basically designed for a vehicle which is running while maintaining a constant speed. An operation to increase or decrease the speed, that is, to change the speed of the vehicle, is carried out by the driver by operating a switch. For this reason, it is necessary for the driver to frequently carry out a manual operation on the switch in a circumstance wherein the speed of the vehicle or the distance from this vehicle to a car running ahead of this vehicle, which is also referred to hereafter as a car-to-car distance, changes frequently as is the case with a vehicle running on a city road. In addition, when the car running ahead of the vehicle reduces its speed all of a sudden, causing the distance from the vehicle to the preceding car to be shortened suddenly, deceleration by the auto cruise control apparatus alone will not be fast enough. When this happens, it is necessary for the driver to apply a brake in most cases. Further, as the brake is applied, the auto cruise control is suspended inadvertently. In order to resume the auto cruise control, it is again necessary for the driver to operate the switch.
The problems described above prove that the auto cruise control is inconvenient in a variety of respects. The application scope of the auto cruise control apparatus is limited to highways in which the amount of traffic is relatively small. As on-board equipment, the auto cruise control apparatus thus lacks appeal or user friendliness.
On the other hand, the research of a so-called ICC (Intelligent Cruise Control) apparatus has been conducted aggressively in recent years. An ICC apparatus is a type of equipment which is capable of detecting a distance from a vehicle using the ICC apparatus installed therein to a car running ahead of the vehicle or the speed of the preceding car relative to the vehicle by means of a radar installed on the vehicle or the like, allowing the vehicle to accelerate and decelerate automatically, that is, to adjust the speed thereof automatically, so as to maintain a safe distance from the vehicle to the preceding car. The ICC apparatus is disclosed in, among other documents, Japanese Patent Laid-open No. Hei 5-221253.
Since this ICC apparatus is still at a research stage, however, a variety of problems encountered in putting the apparatus to practical use will have to be solved. Even if control is exercised so that the distance from a vehicle with an ICC apparatus installed therein to a car running ahead of the vehicle can be maintained at a target value, for example, there will still be a problem as to whether or not the vehicle is controlled by the ICC apparatus in accordance with the driving sense of a human being and whether or not the control using the ICC apparatus results in a sense of incompatibility.
In addition, in the course of a cruise on an ordinary city road, the traffic condition changes often due to, among other causes, moving and stopping in accordance with a traffic light, a transition from one traffic lane to another made by a car running ahead of the vehicle, an interruption by a car running behind the vehicle, passing by another car and crossing a center line by an opportunity traveling car. However, it is still difficult to say that a control system embracing the contemporary technology has reached a level at which the system is capable of controlling a vehicle so as to operate the vehicle with a high degree of safety and accuracy in keeping up with all such traffic circumstances. Thus, if the vehicle can not keep up with a change in traffic condition, that is, for example, if an imminent rear-end collision of the vehicle with a preceding car can not be avoided by relying only on the decelerating power of the ICC apparatus, it is necessary for a safe-driving support system to provide the driver with accurate information in order to let the driver carry out a proper operation.